Screening of Seed-Borne Aspergillus flavus Isolates for Aflatoxin Production in Pulses

The present investigation demonstrated that seed-borne Aspergillus flavus isolates associated with pulse seeds possess variable aflatoxin-producing potential. A total of 15 isolates obtained from gram, pigeon pea, green gram, black gram and lentil were screened for aflatoxin production using GN medium and seed-meal medium. The results showed considerable variation in aflatoxin production among isolates, indicating that the presence of A. flavus on pulse seeds does not necessarily imply an identical level of aflatoxin-producing ability.   Among the isolates examined, GRAF-1 from gram, PPAF-1 and PPAF-2 from pigeon pea, and LAF-1 from lentil exhibited comparatively higher aflatoxin production. In contrast, BGAF-1 produced only a low level of aflatoxin on seed meal, while GRAF-3, GGAF-3 and LAF-3 did not produce detectable aflatoxin on seed-meal medium but showed production on GN medium. These observations clearly demonstrate the influence of both fungal strain and growth substrate on aflatoxin production.   The study further indicated that seed-meal substrates differed in their suitability for aflatoxin production. Gram and pigeon pea supported comparatively greater production, whereas black gram was relatively less favourable. The differences observed between GN medium and seed-meal medium also suggest that substrate composition plays an important role in determining the expression of aflatoxigenic potential.   Overall, the findings emphasize that screening individual A. flavus isolates is more informative than simply determining the occurrence of the fungus in pulse seeds. Identification of highly aflatoxigenic isolates is important for assessing potential food-safety risks and for developing appropriate strategies for safe seed handling, drying and storage. Further studies involving quantitative estimation of individual aflatoxins, characterization of toxigenic and non-toxigenic isolates, and evaluation of environmental factors influencing toxin production would strengthen the understanding and management of aflatoxin contamination in pulses.

Ahmad, S. K. (1993). Mycoflora changes and aflatoxin production in stored blackgram seeds. Journal of Stored Products Research, 29(1), 33–36.   Anilkumar, T. B., & Urs, S. D. (1976). Production of toxic metabolites by seed-borne fungi in sunflower oil. Seed Journal, 6(2), 46–47.   Ashworth, L. J., Jr., Schroeder, H. W., & Langley, B. C. (1965). Aflatoxins: Environmental factors  governing  occurrence  in  Spanish  peanuts. Science,  148(3674),  1228–1229. https://doi.org/10.1126/science.148.3674.1228 Bampton, S. S. (1963). Growth of Aspergillus flavus and production of aflatoxin in groundnuts. Tropical Science, 5(2), 74–81.   Begum,      F.,    &    Samajpati,     N.    (2000).    Mycotoxin     production    on    rice,                  pulses     and oilseeds. Naturwissenschaften, 87, 275–277. https://doi.org/10.1007/s001140050720   Branstad-Spates, E. H., Rajasekaran, K., Wyman, E. M., Sickler, C. M., Carter Wientjes, C. H., & Lebar, M. D. (2025). Evaluation of aflatoxin contamination in protein-rich pulses using a  GFP-expressing Aspergillus  flavus strain. Frontiers  in  Microbiology,  16, 1587035. https://doi.org/10.3389/fmicb.2025.1587035   Codner, R. C., Sargeant, K., & Yeo, R. (1963). Production of aflatoxin by the culture of strains of Aspergillus flavus-oryzae on sterilized peanuts. Biotechnology and Bioengineering, 5(3), 185–192. https://doi.org/10.1002/bit.260050303   Cole, R. J., & Cox, R. H. (1981). Handbook of toxic fungal metabolites. Academic Press.   Deo, P. P., Gupta, C. S., Singh, S., & Gupta, P. (1981). Screening of aflatoxigenic strains of Aspergillus flavus associated with stored seeds of lentil in Agra. Acta Botanica Indica, 9, 331–334.   Diener, U. L., & Davis, N. D. (1966). Aflatoxin production by isolates of Aspergillus flavus. Phytopathology, 56(12), 1390–1393.   Food and Agriculture Organization of the United Nations. (2004). Prevention and control of mycotoxins in foodgrains in India. FAO.